The purpose of this project is to investigate the development of language comprehension in mildly mentally retarded and normally developing children. Language comprehension involves the selection and coordinated use of cognitive, social, and linguistic skills in a goal-direct manner and may be especially problematic for retarded individuals. The studies planned are conceptualized within the Bach and Harnish (1979) model of comprehension. In this model, the goal of comprehension is to identify the communicative intent, or speech act, conveyed. The speech act includes the intended referents and communicative functions (e.g., assertion, question, promise). Successful speech act comprehension requires more than knowledge of linguistic concepts and rules. The hearer must also make inferences based on appropriate information from the communicative context. Only contextual information mutually shared by speaker and hearer is appropriate. Distinguishing mutually shared information from nonmutual information (i.e., data possessed only the the hearer) requires sophisticated perspective taking skills (i.e., the hearer must evaluate the speaker's knowledge). The ability of retarded and nonretarded children, as hearers, to (a) draw inferences based on the utterance and context and (b) distinguish mutual from nonmutual information in order to identify intended referents and communicative functions will be investigated. In the studies planned, the independent variables will represent variations in contextual information which impose different interpretations on the sentences heard. The contextual variables will include the speaker's goals and the physical properties of the objects referred to. Both mutual and nonmutual information will be available to the hearer in some studies. Contextual information will be varied within subjects. The involvement of perspective taking in comprehension will be explored. The subjects will be retarded and nonretarded children at each of three MA levels: 5, 7 and 9. Retarded-nonretarded comparisons will involve groups matched on nonverbal MA and linguistic maturity. Within the retarded and non-retarded levels, IQ's will be equivalent across the different developmental levels. The studies will be conducted according to a repeated measures factorial design. Results will be analyzed by analyses of variance, simple effects tests, and Newman-Keuls comparisons to identify differences across subject groups and experimental conditions. t tests will be used to determine if performance differs from hypothesized standards.